When dimensioning electrical plants for high voltages for seismic regions, it is necessary to design the current paths between the different apparatuses in such a way that the apparatuses, in case of large oscillations, are not exposed to abnormally great forces at the points of connection.
The problem arises particularly in connection with valve halls in plants for high voltage direct current, in which the valves are suspended from the roof to protect them against seismic stresses (see U.S Pat. No. 4,318,169). In such plants, the oscillation amplitudes may become relatively great, up to about .+-.1 m, and special arrangements must therefore be made to make the oscillations of the current paths controllable so as to be able to maintain the operation also during and after an earthquake.
Making the flexible connectors between the transformer and the valve assemblies, in a plant as described in the above U.S. patent, in the form of slack conductors would require unreasonably large phase distances. For that reason, a design for the above-mentioned purpose has been proposed which comprises two coaxial tubes which are telescopically displaceable relative to each other and which, at their outer ends, are attached to the valve assembly or the transformer bushing in question by means of cardan or ball joints, which are electrically bridged by means of copper strands. The electrical connection between the two tubes takes place via a flexible copper band which is arranged inside the tubes and mounted in the form of a loop over two spaced-apart rollers. A drawback with this design is that the tubes have to be perforated to attain sufficient cooling of the enclosed connection. This in turn leads to a deterioration of the current-carrying capacity and the mechanical stiffness of the tubes.